Sulfur dioxide(SO.sub.2) exhausted from combustion of fossil fuel pollutes air and acid rain containing SO.sub.2 causes soil and water pollution. Accordingly, removal of SO.sub.2 before emitting flue gas into the atmosphere has been regarded as an important matter, as the consumption of fossil fuel increases.
For the removal of SO.sub.2, the following two methods have been suggested in the art: one is to prevent the generation of SO.sub.2 itself by desulfurizing the fossil fuel prior to the combustion; and, the other is to remove SO.sub.2 from the flue gas using appropriate sorbents, which can be further classified into dry method and wet method depending on the type of sorbent.
In accordance with the wet method, SO.sub.2 is directly taken up by liquid sorbents such as water, alkali solution, which facilitates efficient removal of SO.sub.2 with relatively inexpensive sorbents. However, the problem of disposal of wastes such as solid materials produced from the reaction with SO.sub.2 and waste water remains unsolved.
On the other hand, in accordance with the dry method, SO.sub.2 is removed by solid sorbent whose surface area is relatively large. This method has several advantages over the wet method that: no waste occurs and the expenses for equipment and operation may be cut down, since the sorbent can be regenerated and reused; and, the pure SO.sub.2 produced from the regeneration step can be utilized as pure sulfur or sulfuric acid after appropriate treatment. However, it has revealed a shortcoming that sulfur removal efficiency is extremely low, since SO.sub.2 is reacted with the sorbent for a relatively short time period compared with the wet method.
Naturally, many studies have focused on the development of a novel sorbent employed for dry method, which has a high SO.sub.2 sorption capacity. For example, Centi et al. discloses a .gamma.-Al.sub.2 O.sub.3 sorbent impregnated with metal oxides (see: Centi et al., Ind. Eng. Chem. Res., 31:1947(1992)), where SO.sub.2 is taken up by the sulfation of the metal oxides to give metal sulfides. Among the metal oxides, copper oxide(CuO) has been used as the most promising one, since it reacts with SO.sub.2 rapidly and has a relatively high SO.sub.2 removal capacity. However, the prior art sorbent is proven to be less satisfactory in the sense that the SO.sub.2 removal capacity is not sufficient enough to be realized in industrial application. Under the circumstances, there are strong reasons for developing an alternative sorbent which has a superior sulfur removal capacity and a high regeneration conversion rate.